Group 2 innate lymphoid cells in health and disease.

Group 2 innate lymphoid cells (ILC2s) play critical roles in anti-helminth immunity, airway epithelial repair, and metabolic homeostasis. Recently, these cells have also emerged as key players in the development of allergic inflammation at multiple barrier surfaces. ILC2s arise from common lymphoid progenitors in the bone marrow, are dependent on the transcription factors RORα, GATA3, and TCF-1, and produce the type 2 cytokines interleukin (IL)-4, IL-5, IL-9, and/or IL-13. The epithelial cell-derived cytokines IL-25, IL-33, and TSLP regulate the activation and effector functions of ILC2s, and recent studies suggest that their responsiveness to these cytokines and other factors may depend on their tissue environment. In this review, we focus on recent advances in our understanding of the various factors that regulate ILC2 function in the context of immunity, inflammation, and tissue repair across multiple organ systems.